The present invention relates to a process for preparing a glass fiber reinforced cementitious substrate.
Asbestos cementitious substrates have been used as substrates having high strength in thin thickness and excellent non-combustible property and have been prepared in mass production.
However, the coventional asbestos cementitious substrates have disadvantageously low impact strength and have been broken by certain shock of stone and others when the asbestos cementitious substrate is used for a soundproof wall, a chimney, a roof or the like.
In order to increase the strength, it has been proposed to increase a content of asbestos. However, it has not succeeded to give enough impact strength. On the other hand, it has not desirable to increase the content of asbestos from the viewpoint of pollution and resources.
Pulp cementitious substrates have been also used for the same purposes, however, they have been unsatisfactory from the viewpoints of impact strength and noncombustible property.
It has been considered to blend synthetic fibers, rock wool, slag wool or the like as well as asbestos or pulp.
However, they have been also unsatisfactory and have not been practically used.
Recently, glass fibers having alkali resistance have been developed and glass fiber reinforced cementitious substrates have been practically used.
The glass fiber reinforced cementitious substrates have high bending strength and high impact strength even though a content of glass fiber is small in comparison with the other fibers such as asbestos. However, it has not been succeeded to attain a mass production by the sheeting method.
When a slurry of cementitious material containing only glass fiber has been used in the sheeting method, like Hatchek process, magniani process or etc. a vat level has been too low to operate the sheeting method. When the tests have been carried out by increasing a feeding rate of the slurry or the like, the times for taking up on making roll have been remarkably increased, and the product has been easily peeled off at each layer and the strengths of the product has been too low for a practical use. The inventors have studied to prepare glass fiber reinforced cementitious substrates by the sheeting method.
The followings are the definitions of the terms used in the specification.
Wet film: a slurry is filtered to remain wet solid components on a wire or felt in a form of wet film. PA0 Green sheet: a wet film is wound on a making roll to give a tubular wet sheet, which can be cut to form a plane sheet. PA0 Cementitious substrate: a green sheet is cured to form cementitious substrate.